That's a good way! Alcohol is easy because it doesn't go bad and evaporates by itself.
Food: some people leave until it goes bad (seems gross to me but it's a common method), some people just overnight. Some people bury the offerings afterwards, some people just wrap them respectfully in tissue and throw them out. (I live in a 6th floor city apartment; sometimes the choice is practical rather than spiritual)
Another common alternative is to share a meal/drink with the spirit (so consuming the offerings yourself, but in a very slow, mindful way, and offering the taste and experience up to them). (This is completely different from leaving a piece of cake as an offering, getting hungry later and going "uh... actually this is one of those shared offerings!")
It depends on the tradition, the practitioner, and the individual spirit. My UPG is that Venusian-type spirits want you to have the sensory experience (ie, consume the offering) and to witness you having it.
If you're not sure, you can use simple divination (eg pendulum, coin-flipping or
prayer-bead divination) to ask if your planned method is pleasing to them.
