1.One way to make your car smell good is to use an air freshener. However, many people find the smell too strong and they may even have an allergic reaction in terms of coughing or sneezing if they are very sensitive to it. Whatever the case, these are some of the options you use:
-Air freshener sprays
-Hanging air fresheners
-Clip-on air fresheners on the vents
-Electric air fresheners
-Ioniser air fresheners
All of these options have there advantages, a spray will instantly cover bad smells for example, while an Ioniser may be a bit more of an investment but it actually cleans the air to remove the bad smells completely.
2.In many cases, your car smells bad because you aren't looking after the air conditioning system properly, and as a result bacteria multiply, causing an unpleasant odour, especially when your turn on the air conditioning. Read more on motor.onehowto.