By anything I don't mean to put some random liquid in a car engine, but is it possible to design and build an engine or motor that could use something like tea or orange juice for it's fuel? I know it won't be practical or even efficient, but if someone were to do it just for the sake of doing it, would it be possible?
The first consideration behind a fuel choice is its energy density and specific energy - that is, how much energy can you extract from a kilogram or liter of the fuel, by whatever means the energy is extractable.
You can use hot tea as heat source to extract some usable work using a Stirling engine. You could use acids of orange juice to generate electricity in a battery, or somehow extract and burn its sugar. There's absolutely no way to build anything reasonably usable as a car around that though - simply, the energy extracted is so small it's pointless, the milleage would be beyond garbage - it's dubious a tank full of hot tea would manage to get the car out of the garage into the driveway.
So, only high-energy fuels and means of energy storage are considered for practical uses. And you can extract energy from a lot of materials. Oils, fats, wood, methane, explosives, all kinds of highly reactive chemicals, radioactives, extremely compressed substances, and so on.
At this point other considerations must be made - primarily cost of the fuel per unit of energy, safety, environmental factors and practicality of the energy source. But if you disregard these, you can power motors from a staggering range of energy sources.
The first diesel engine actually used peanut oil as the fuel so yes, you can design an engine around the fuel.
Not too long ago in Wales, cooking oil was very cheap and a supermarket was selling many 1000’s of litres. The police and customs noticed and quite a few were prosecuted for running diesel cars on veg oil - because they were not paying the fuel duty.
Flour suspended in air can be explosive, but designing a method to use it as a fuel may prove tricky...