If the two separate businesses are not interrelated, but completely separate entities, then you should file two separate businesses on your tax return. In other words, each business derives it's income separately and the expenses are unique to each business.
If you find that each business is dependent upon each other to produce revenue, you can choose to file it as one business with two sources of income. In record keeping you can track it separately, then on the tax return you can combine the full amount as receipts for business.
You can be a sole proprietor in several business ventures.
