You can kinda sorta get close using EQ, but if you really want to do it right, you'll need to get into impulse responses.
If you want a really simple, really expensive option with all the bells and whistles, then check out Speakerphone by AudioEase.
If you are on a budget, or prefer the DIY approach, you will first need a convolution reverb plug-in. It will take a recording of an impulse response (which sounds like a starter pistol), and then apply that reverb to the sounds that you wanted to apply to. If you need a free option, Reaper has a plug-in called ReaVerb that is free, and I think they have a version of that plug-in that works with other DAWs as well.
Then you'll need to search for an impulse response of a radio, and use that.
Optionally, if you really want it to sound like it's being played in a bar, find another impulse response that gives an impression of the room - what you think the bar should sound like.
You can layer them, so it sounds like it's being played from a radio, in the environment of a bar. And when done right, it will be absolutely impossible to tell whether was the real thing or simulated through plugins.
I would start with a low pass filter and then EQ until it sounds about right.
You can kinda sorta get close using EQ, but if you really want to do it right, you'll need to get into impulse responses.
If you want a really simple, really expensive option with all the bells and whistles, then check out Speakerphone by AudioEase.
If you are on a budget, or prefer the DIY approach, you will first need a convolution reverb plug-in. It will take a recording of an impulse response (which sounds like a starter pistol), and then apply that reverb to the sounds that you wanted to apply to. If you need a free option, Reaper has a plug-in called ReaVerb that is free, and I think they have a version of that plug-in that works with other DAWs as well.
Then you'll need to search for an impulse response of a radio, and use that.
Optionally, if you really want it to sound like it's being played in a bar, find another impulse response that gives an impression of the room - what you think the bar should sound like.
You can layer them, so it sounds like it's being played from a radio, in the environment of a bar. And when done right, it will be absolutely impossible to tell whether was the real thing or simulated through plugins.
FM transmitter and play it through a radio?
https://en.m.wikipedia.org/wiki/FM_transmitter_(personal_device)
Pass it through a tin can.