I have a 2003 mazda b3000 3.0.(with a ford ranger engine obviously). I let it get too low on gas, filled up at a shell station and not 5 minutes later it started running very sluggishly and check engine light popped on. Had it checked it came back as a misfire on cylinder 5 so I did all the basics, changed spark plugs and wires, fuel filter and coil pack but engine is still sluggish....

 

Welcome to the forum

Add some HEET or Octane Boost to the gas in the tank, both are methanol based which will remove water from the gasoline.

All gasoline contains some water, "bad gas" is when there is too much water.
Water and gasoline can't mix/bond, and water is heavier than gasoline so will settle to the bottom of the tank, where fuel pump is, so you are getting a higher percentage of water.
Methanol, or ethanol, CAN bond with water so will make the water "burnable", less likely to cause misfires/sluggishness

My guess is you got some "bad gas", so add some methanol and see how it goes.