Business Tax write-offs

You can expense vacation costs that are business related, if those expenses you paid were necessary and reasonable business expenses. Which could include things such as meals, airlines, hotels, etc.

Here is an TurboTax article regarding side gigs:

https://turbotax.intuit.com/tax-tips/self-employment-taxes/side-giggers-tax-tips-for-side-jobs/L6025l8Uh## 

You can deduct business-related expenses such as legal & professional fees, business licenses, postage for a side gig.

You can deduct the either the actual expenses or mileage on your vehicle, but not both, if it is a sole proprietorship schedule C.

You will need & signed & dated accountable plan for a S corp or partnership, to deduct actual vehicle expenses that are from a vehicle that is not under the business' name. 

You  can deduct the "business" related expenses for your internet and phone, but not the personal expenses.