Can we file skip the dishes income of $5000 on form t2125 or should we include this income in other income on line 104

That is only correct if Skip the Dishes has been determined to be a taxi business. I don't believe it has been designated that way although I could be wrong. Skip the Dishes seems to be more of a delivery service, in which case the small supplier threshold applies.

It might not be mandatory to apply for a BN since the sales are still less than $30,000, but why not handle it as a business from the start? Certainly any expenses incurred to earn the income, including reasonable vehicle costs, would be deductible.

you don't need to be registered for a business number to use T2125; this is small business income, deduct the costs it took to get there as long as they have an expectation of profit

There was a discussion in the TaxCycle forum just last week about the GST/HST issue surrounding Uber and Uber Eats drivers.  

The resolve was that taxi services are automatically required to register and collect GST/HST as soon as they reach their first $1.00 of income, so all Uber drivers would fall in this category.  If the Uber Eats driver is also an Uber driver, then GST/HST needs to be collected: "a person or business who is registered for HST can not decide which of their sales they will collect tax on and which they won’t."  

If, on the other hand, the Uber Eats driver's only income is from delivery services (no taxi services) and they are not registered for GST/HST, then GST/HST is not required while their income is below the $30K threshold.