In a homebrew campaign I'm running, I decided to make a bakery in the main town the party is staying in. While the bakery has some normal stuff you'd find at a bakery, it also has some arcane treats as well. Problem is... well I'm stumped. A lot of stuff I find online are either magic in description (EX: a cake that will always taste like your favorite flavor) or something players might find unhelpful for the players (EX: a cookie that polymorphs the player into a rat or something).

I've made a couple of helpful ones, like a box of chocolate truffles that heal 2 hp per truffle but I'm having trouble coming up with other ideas. They don't need to be healing or anything, but I want them to be both interesting from a roleplay perspective and useful in a combat situation. Any help or ideas are appreciated!

Well, you could always go to the magic item list, filter for consumable items, and re-flavor some of them as baked goods?

Some suggestions from that: Mind Crystal (basically grant one-shot meta-magic), or various fun potions like Potion of Resistance, Potion of Heroism, or even Blood of the Lycanthrope Antidote if you need it for story purposes.....

I like your idea of 2 hp per truffle, and you can build on it by creating more treats that mimic potion effects, just not as effectively.

I like to go overboard, so here are three ideas and a format you can use to design more:

Pixie Puffs
Light, airy pastries dusted with sparkling sugar that seems to twinkle in the light. Each bite melts in your mouth, leaving a faint, pleasant tingle.

Effect:
Invisibility Glimmer: For the next minute after consuming a Pixie Puff, the eater gains a faint, shimmering outline. This outline grants advantage on Stealth checks to hide but does not confer true invisibility. If the eater makes an attack or casts a spell, the effect ends immediately.

Dragonfire Taffy
A chewy, spicy candy with swirling red and orange stripes. When unwrapped, it smells of smoke.

Effect:
Warmth of the Wyrm: For the next minute after consuming a piece of Dragonfire Taffy, the eater becomes resistant to cold. Additionally, the eater can produce a small, harmless flame from their fingertip, sufficient to light candles or campfires. This flame lasts for up to 1 minute and can be extinguished at will.

Moonlit Marzipan
Soft, almond-flavored sweets molded into the shape of crescent moons, glowing faintly with a silvery light.

Effect:
Lunar Insight: For the next minute after consuming a piece of Moonlit Marzipan, the eater gains a +1 bonus to Wisdom (Perception) checks. Additionally, the eater can see in dim light as if it were normal light for the duration.

A large cake that acts as a Hero's Feast when eaten seems an obvious (though expensive!) option. 

Pretty much I'd say just look at potions and convert those to fun sounding treats instead. You already got partly there with the truffles - how about a red velvet cake pop that grants fire resistance for an hour?

Prank sweets which change your vioces could work if your group is the sort to roll with it.

• a gobstopper which gives advantage on concentration checks whilst you're eating it, but denies you verbal components or talking.
• liquorice which makes your tongue shine like a bullseye lantern for 10 minutes. The range gets shorter over time.
• concentrated cinnamon candies which cast Dragons Breath on you for one round.
• sweets which increase or decrease the volume of your voice for a time (thaumaturgy)
• Chews which let you speak (exclusively) to animals for a time.
• Magical chewing gum. Constitution checks to increase the size. Works like Web spell if popped.
• different coloured sherberts which let you reroll a damage dice for different damage types (EG orange sherbert lets you reroll one fire damage dice)
• Messaging hard candy. Whilst you're eating it, you can communicate telepathically with someone else eating it (break in half before using). Actually give the players boiled sweets - if they finish them, the magic ends.

A honeybee that functions like the fireball spell if thrown, or if eaten, deals 6d8 fire damage.

A gobstopper that never dissolves. Spellcasters who have this in their mouth have difficulty casting spells with a verbal component.

Bubble Gum - Allows you to float a foot off the ground if you blow a bubble with it.

Gummy Candy - Makes your skin elastic reducing damage by 1 for 1 round.

Candy Cane - Bonus Action to sharpen into a 1 use dagger.

Sugar Buttons - Change the color of your skin.

Doh-nut - The consumer loses memory of the last minute.